JPS61136589A - Preparation of tar acid - Google Patents

Abstract

PURPOSE:To enhance the yield of a tar acid product by recovering and mixing Glauber's salt separated from crude phenol after sulfuric acid decomposition, wash water from the crude phenol and water obtd. by dehydrating the crude phenol, and allowing the resultant mixture to stand. CONSTITUTION:When tar acid is prepd. from coal tar-derived crude phenolate, Glauber's salt obtd. after sulfuric acid decomposition, wash water from crude phenol after the sulfuric acid decomposition and water obtd. by dehydrating the crude phenol by distillation are mixed in a recovery separator. A crude phenol recovery rate and a tar product yield are increased by allowing the resultant mixture to stand, recovering the separated crude phenol and subjecting it together with crude phenol recovered after sulfuric acid decomposition to a water washing process.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing tar acid from coal tar, and more particularly to a method for improving the recovery rate of tar acid.

BACKGROUND ART Conventionally, as a method for producing tar acid from coal tar, a method as shown in the flowchart of FIG. 1 has been known. In the method shown in FIG. 1, crude phenolate is obtained by first adding caustic soda to carbon oil and naphthalene oil obtained by distilling coal tar to deoxidize them. Next, this crude phenolate is subjected to a dumping treatment with steam to remove impurities such as neutral components and base components, and then decomposed with sulfuric acid to obtain crude phenol. Next, a tar acid product can be obtained by distilling the masticated phenol after washing with water and dehydration.

However, in this method for producing tar acid, the recovery rate of tar acid is not satisfactory due to the following problems.

b) In the process of separating crude phenol and Glauber's salt based on the difference in specific gravity after sulfuric acid decomposition, crude phenol is entrained on the Glauber's salt side.

Mouth) After washing the crude phenol with water, in the process of separating the original phenol from the water due to the difference in specific gravity, a large amount of the original phenol is contained in the water side.

c) A large amount of phenol is entrained in water during the evaporation and dehydration process after washing with water.

In addition, since the mirabilite and water obtained in steps a) to c) above contain a large amount of crude phenol, conventionally, the mirabilite and water were processed by the activated sludge method after or without recovering the mirabilite. Although wastewater treatment is being carried out, there are also problems in that the amount of wastewater to be treated is large and the processing load is high.

--Method for Solving Problems The present inventor has conducted intensive research to find a method for improving the recovery rate of tar acid in a method for producing tar acid from coal tar, and found that after sulfuric acid decomposition, By collecting the water obtained by dehydrating the mirabilite separated from the crude phenol, the water for washing the antiphenol, and the water obtained by dehydrating the crude phenol, the crude phenol and the mirabilite water are separated by the salting out effect. It was found that the results were good and that crude phenol could be efficiently recovered. The present invention is based on this knowledge.

That is, the present invention, when producing tar acid from crude phenol derived from coal tar, uses:
Production of tar acid characterized by mixing water obtained by evaporative dehydration of crude phenol in a recovery separator, leaving it to stand, recovering the separated crude phenol, and subjecting it to a water washing process together with the phenol after decomposition with sulfuric acid. Pertaining to law.

A flowchart of the method for producing tar acid according to the present invention is shown in FIG.

In the method of the present invention, crude phenol is obtained by first subjecting coal tar to distillation, deacidification, dumping, and decomposition with sulfuric acid in the same manner as in the conventional method.

The processing conditions up to sulfuric acid decomposition may be the same as those of conventional methods, and no special conditions are required.

After decomposition with sulfuric acid, crude phenol and Glauber's salt are separated based on the difference in specific gravity. The obtained Glauber's salt is accompanied by about 0.6 to 1% of sodium sulfate, and since the crude phenol after decomposition with sulfuric acid sent to the recovery separator contains a small amount of Glauber's salt, the Glauber's salt is removed by washing with water. The washing water is separated from the crude phenol due to the difference in specific gravity, but since the water side contains about 3 to 5% crude phenol, the washing water is sent to the recovery separator.

After washing with water, the water content of the crude phenol is removed by evaporation and dehydration. Since the water obtained by evaporative dehydration contains approximately 3 to 6% of crude pheno-e, this water is also sent to the recovery separator.

Then, the evaporated and dehydrated crude phenol is distilled according to a conventional method to obtain a tar acid product.

In the recovery separator, the mirabilite separated from the ground phenol after decomposition with sulfuric acid, the washing water of the crude phenol, and the water obtained by evaporation and dehydration of the crude phenol are combined and allowed to stand.

Since this recovered mixture contains a large amount of Glauber's salt, the salted phenol is easily separated from the Glauber's salt water due to the salting out effect. The conditions for the recovery separator vary depending on the nitrate concentration, crude phenol 4 degrees, etc., but the temperature is usually 40 to 80 degrees Celsius.
It is sent to a water washing process along with the crude phenol that can be dissolved, and is used in the production of tar acid.

0 in the recovered mixture before separation into crude phenol and mirabilite water.
．． It contains about 8 to 1.5% crude phenol, but after separating the crude phenol using the salting out effect, the sodium sulfate solution contains 0.
．． It only contains about 6% of primary phenols. Therefore, there is an advantage that the recovery rate of crude phenol is improved and the processing load can be reduced when activated sludge treatment is performed after recovering mirabilite from 1-milk salt water or without recovering mirabilite.

According to the method of the present invention, the yield of tar acid products is improved by improving the recovery rate of crude phenol. Furthermore, by reducing the amount of crude phenol contained in wastewater, the load on activated sludge treatment can be reduced.

Example The present invention will be described in detail below with reference to Examples.

Example 1 Coal tar was subjected to distillation, deacidification, and dumping treatments according to conventional methods to obtain a crude phenolate containing 20% acidic content.

Using this crude phenolate as a raw material, crude phenol was produced and recovered according to the flowchart shown in FIG. 8 by the method shown below at a processing rate of 150 tons/day. First, crude phenolate 50t/day 66% sulfuric acid 7. After adding Lt for 1 day, the mixture was decomposed with sulfuric acid and separated into Glauber's salt and crude phenol. This Glauber's Salt contains 0 crude phenol.
．． 4 tons/day of crude phenol was produced in 1.5 tons of water containing Glauber's salt.
It was accompanied by 8 tons/day. The crude phenol was then mixed with water 5.
7 t/day of water washing, 9.4 t/day of crude phenol containing 1.8 t/day of water and 5.7 t/day of washing water containing 0.2 t/day of crude phenol (jl phenol content 8.4%) ) and obtained. Next, this water-containing crude phenol is evaporated and dehydrated to yield 9 Jt/day of crude phenol containing 0.1 t/day of water and 1.6 t/day of water containing 0.1 t/B of crude phenol (crude phenol content 5.8%). ) and separated.

The glauber's salt containing crude phenol obtained by sulfuric acid decomposition and the water containing crude phenol obtained from the water washing and dehydration steps are collected and mixed in a recovery separator, left to stand, and separated into crude phenol and mirabilite water using a sulfuric device. .4 t/day of crude phenol could be recovered.

In addition, mirabilite solution contains only 0.3t7-day crude phenol, and the crude phenol content in mirabilite solution is 0.6%.
and decreased.

As is clear from the above results, in the method of the present invention, the amount of crude phenol recovered increased by 0.4 t/day compared to the conventional method, and the crude phenol content in the mirabilite solution was 1.5 tons/day before the crude phenol recovery. 8%, but after crude phenol recovery, ζ
It was reduced to 0.6%.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of the tar acid production process according to the conventional method, and FIG. 2 is a flowchart of the tar acid production process according to the method of the present invention. FIG. 3 is a flowchart of the process of producing crude phenol from the crude phenolate of Example 1. (or more) 〉=7...

Claims (1)

[Claims] (1) When producing tar acid from crude phenolate derived from coal tar, i) Glauber's salt obtained after decomposition with sulfuric acid, ii) washing water of crude phenol after decomposition with sulfuric acid, and iii) obtained by evaporative dehydration of crude phenol. A method for producing tar acid, which comprises mixing water in a recovery separator, allowing it to stand, recovering the separated crude phenol, and subjecting it to a water washing process together with the crude phenol after decomposition with sulfuric acid.